ESP: AES_192 ciphers only supported on esp32 and S2

[petermm]

As surfaced from expanded CI the AES 192 ciphers as configured only works on esp32 and esp32-S2.

A code search on esp-idf seems to confirm this: https://github.com/search?q=repo%3Aespressif%2Fesp-idf%20SOC_AES_SUPPORT_AES_192&type=code

One can enable the ciphers with this build config CONFIG_MBEDTLS_HARDWARE_AES=n, but obviously not preferable.

It returns MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED https://github.com/espressif/esp-idf/blob/e4f167df2504544d6f46655228634549c3d0d9c2/components/mbedtls/port/aes/esp_aes_common.c#L68

So figure out gracefully handling it and documenting it.